Contribution of white clover varieties to total sward production under typical farm management

White clover varieties, potentially suitable for inclusion in seed mixtures for mixed stock-rearing farm systems, were evaluated when growing with S23 perennial ryegrass under rotational sheep grazing with a silage cut in late May or early June, as practiced on farms. Monoculture grass swards were also included to enable the direct and indirect contribution of white clover to total sward production to be evaluated.
White clover increased total sward production during all three years of the trial by an average of 50%. Although clover content of swards were similar, large differences occurred in their grass content, especially in the third year, when difference in total yields of swards based on large–leaved clover varieties was 2 t ha ⁻¹ while difference in clover yield was only 0-6 to ha^–1 The indirect contribution of white clover, namely the extra grass resulting from N transfer, was greater in the spring than in the autumn. It was also greater for Nesta than for other varieties. and exceptional for this variety in that the increase in grass yield above that of grass monoculture was maintained over three harvest years.     

The effect of dietary n-3 and n-6 fatty acid balance on the growth of the prawn Penaeus monodon

A post-hoc study of the influence of dietary fatty acids of the n-3 and n-6 series on the growth of the prawn, Penaeus monodon showed a clear example of interaction by these nutrients to influence growth. Data from three independent growth studies examining the dietary requirements for linoleic (LOA, 18:2n-6), linolenic (LNA, 18:3n-3), arachidonic (ARA, 20:4n-6), eicosapentaenoic (EPA, 20:5n-2) and docosahexaenoic (DHA, 22:6n-3) acids were standardized through a common reference to allow comparison. Analysis of the variation within the experiments was able to define effects attributable to the individual experiments or the overall dietary n-3 and n-6 levels. A generalized additive model (GAM) indicated that both parameters (experiment, and n-3 and n-6 levels) had significant ( P  < 0.05) effects on growth. Loess nonparametric modelling of the data clearly demonstrates `the effect of relationship' on prawn growth to the levels of dietary n-3 and n-6 fatty acids. The response surface model shows clear effects of both n-3 and n-6, and that the effect of n-3 changes with the level of n-6 (and vice versa). Parametric examination of the relationship ( y =–37.149 x ³ + 160.84 x ² – 118.64 x  + 290.6, r ²=0.492, P  < 0.05) between growth and the ratio between the two fatty acid classes suggested that the optimal ratio of n-3 and n-6 fatty acid is about 2.5 to 1. The results of this study demonstrated that the interaction of the dietary n-3 and n-6 fatty acid classes is an important factor of prawn fatty acid nutrition.     

The transmission potential of Rift Valley fever virus among livestock in the Netherlands: a modelling study

Abstracts

Rift Valley fever virus (RVFV) is a zoonotic vector-borne infection and causes a potentially severe disease. Many mammals are susceptible to infection including important livestock species. Although currently confined to Africa and the near-East, this disease causes concern in countries in temperate climates where both hosts and potential vectors are present, such as the Netherlands. Currently, an assessment of the probability of an outbreak occurring in this country is missing. To evaluate the transmission potential of RVFV, a mathematical model was developed and used to determine the initial growth and the Floquet ratio, which are indicators of the probability of an outbreak and of persistence in a periodic changing environment caused by seasonality. We show that several areas of the Netherlands have a high transmission potential and risk of persistence of the infection. Counter-intuitively, these are the sparsely populated livestock areas, due to the high vector-host ratios in these areas. Culex pipiens s.l. is found to be the main driver of the spread and persistence, because it is by far the most abundant mosquito. Our investigation underscores the importance to determine the vector competence of this mosquito species for RVFV and its host preference.     

Effect of hCG and eCG Treatments on Prostaglandins Synthesis in the Porcine Oviduct

The oviduct plays a crucial role in fertilization, gamete maturation and embryo transport. Prostaglandins are some of the main factors determining its roles. The present study investigated the influence of oestrus synchronization and superovulation on prostaglandins synthesis in the porcine oviduct. Mature cross‐bred gilts after exhibiting oestrous cycles were divided into four groups: I, cyclic; II, inseminated; III, synchronized and inseminated; and IV, superovulated and inseminated. Oviducts were collected on the third day of the oestrous cycle or after insemination and divided into isthmus and ampullary parts. This study demonstrated lower mRNA (in the isthmus and ampulla; p < 0.05, p < 0.001, respectively) and protein prostaglandin endoperoxide synthase 2 expression (in the isthmus; p < 0.001) in gilts treated with human chorionic gonadotrophin/equine chorionic gonadotrophin (hCG/eCG) compared with Group II that were inseminated only. In addition, hCG and eCG treatment decreased mPGES‐1 mRNA levels in Groups III and IV, in both the isthmus (p < 0.01 in III, p < 0.001 in IV) and ampulla (p < 0.001). The prostaglandin E₂ content of oviductal tissues was significantly lower in Groups III (p < 0.05) and IV (p < 0.01 in isthmus, p < 0.0001 in ampulla) compared with Group II. mRNA and protein levels of PGFS in Group IV in the oviductal isthmus were higher (p < 0.01) compared with the non‐treated Group II. In effect, the amount of prostaglandin F_2α in oviductal tissues of gilts treated with hCG/eCG was significantly elevated (p < 0.001 in isthmus of Groups III and IV; p < 0.05 in ampulla of Group IV). Differential expression of the factors analysed in gilts treated with exogenous gonadotrophins suggests that hCG/eCG stimulation affects prostaglandins synthesis pathway. These changes can alter oviduct functions and in turn affect gamete maturation and fertilization as well as development of embryos and their transport to the uterus.     

Effects of Vasectomy on Seminal Plasma Alkaline Phosphatase in Male Alpacas (Vicugña pacos)

Azoospermia is a common finding in male alpacas which present for infertility. The challenge is to differentiate azoospermia of testicular origin from non‐testicular origin. In several species, alkaline phosphatase (AP) concentrations in seminal plasma have been used as a diagnostic marker of contributions of the testis and epididymis to the ejaculate. The purpose of this study was to determine whether AP assay could differentiate testicular from non‐testicular azoospermia in male alpacas. An experimental model of bilateral outflow obstruction (pre‐scrotal vasectomy) was used in 22 male alpacas, aged 2–9 years. No reproductive history was available. Animals were submitted for electroejaculation (EE) under general anaesthesia and vasectomy performed. Five weeks later, animals were submitted for EE. Vasectomy was not successful in one animal, which was removed from analysis. AP levels were compared in seminal plasma in the pre‐ and post‐vasectomy samples. The mean ± SEM concentration of AP in pre‐vasectomy seminal plasma was 504.29 ± 166.45 U/l (range 10–2910); the post‐vasectomy levels were 252.48 ± 81.77 U/l (range 0–1640; p = 0.06). In 71.4% of animals, AP levels decreased, varying from 18% to 100% reduction. Results of this study suggest that AP is not produced exclusively by the testis and epididymis in alpacas and that AP assay is not a valid diagnostic test for determination of origin of azoospermia; the gold standard for diagnosis of origin of azoospermia remains testicular biopsy.     

Potential seed yield of white clover varieties

Fifteen varieties of white clover were sown in order to assess the seed yielding ability of new and potential varieties and to examine those plant factors which affect seed yield. Counts were made on number of inflorescences m^-2, proportion of ripe inflorescences and other inflorescence and seed characters. The data were used to compute potential seed yields.
Average potential seed yields were 276 and 76 kg ha^-1 in the first and second year, respectively. The decrease in the second year seed yields underlines the overriding effect of adverse weather conditions during the critical June to August period. The major effect was a reduction in the number of inflorescences produced, the number of florets per inflorescence and seeds per floret.
Some of the new listed varieties have a significantly higher seed potential than SI00, e.g. Menna (+ 38%) and Olwen (+28%), and this should facilitate the production of adequate seed supplies of British bred varieties.     

Effects of altitude on circadian rhythm of adult locomotor activity in Himalayan strains of Drosophila helvetica

Background  

We recently reported that the altitude of origin altered the photic and thermal sensitivity of the circadian pacemaker controlling eclosion and oviposition rhythms of high altitude Himalayan strains of Drosophila ananassae. The present study was aimed at investigating the effects of altitude of origin on the pacemaker controlling the adult locomotor activity rhythm of D. helvetica.     

Comparison of Three Clinical Techniques for the Diagnosis of Laryngeal Paralysis in Dogs

Objectives— To evaluate laryngeal function using 3 diagnostic techniques: echolaryngography (EL), transnasal laryngoscopy (TNL), and laryngoscopy per os (LPO).
Study Design— Prospective clinical study.
Animals— Dogs with laryngeal paralysis (n=5) and control dogs (n=10); 5 age- and breed-matched dogs and 5 young, breed-matched dogs.
Methods— Laryngeal function was evaluated in conscious dogs using EL. All examinations were recorded and evaluated by separate, blinded observers upon completion of the study. The methods were compared with a standard evaluation incorporating all clinical knowledge of the case (STD) using sensitivity, specificity, positive, and negative predictive values.
Results— Three dogs with bilateral laryngeal paralysis requiring surgery were diagnosed as unilaterally affected or normal on EL. Three dogs had paradoxic motion on TNL and LPO, 2 of those were considered normal on EL, and 1 had no motion on EL. Paralysis was diagnosed in 1 age-matched and 3 young control dogs on EL. LPO and TNL falsely diagnosed lack of arytenoid movement in 2 age-matched controls and 1 young control. Two age-matched and 1 young control dog were misdiagnosed as paralyzed with TNL and LPO.
Discussion— Direct observation of the larynx allowed better evaluation of laryngeal function compared with EL. TNL did not require induction of anesthesia, but did not improve the ability to assess laryngeal function compared with LPO.
Conclusions— EL was not as effective as direct observation of the larynx. TNL did not improve the evaluation of laryngeal function compared with LPO.
Clinical Relevance— We use LPO combined with knowledge of the clinical history and physical examination to diagnose laryngeal paralysis in preference to EL and TNL.